In the development of security devices for monitoring the entrances to and within a building, door monitoring switches are known which will activate a remote alarm in the security system when the door is moved in relation to the door jamb. Typically, these switch devices are held in the hinge leaves of a door hinge so as to be hidden from view when the door is closed. Hinges of this type may have an abutment surface on one hinge leaf contacting a plunger operating a switch hidden in the other leaf, as shown in U.S. Pat. No. 3,715,537, to Peterson, or U.S. Pat. No. 3,729,603, to Foltz, for example.
A more sophisticated approach to the problem is shown in U.S. Pat. No. 3,806,852 to Suska, in which a magnet hidden by one leaf magnetically operates a switch concealed in the other leaf, the security device thus being completely hidden from view regardless of whether the door is open or closed. Another known arrangement, described in U.S. Pat. No. 3,840,715, to Gwozdz, consists of a switch in the door jamb behind the hinge leaf which is operated by a pushrod concealed in the hinge leaf, the pushrod being driven at one end by a cammed surface on the hinge pin when the hinge pin is rotated during movement of the door with respect to the door jamb. When mortising is required, these switch arrangements, which include projections from the rear surface of the hinge leaf or leaves, increase the cost of using the system.